The term in-ear device includes active as well as passive devices in which all or at least a portion of the device is inserted into the ear canal of the user. The devices may include means for amplification or suppression of sound. Such devices are described in U.S. Pat. Nos. 6,754,357 and 6,339,648 (both of which are herein incorporated in their entirety) in which a rigid or semi-rigid central core component is provided with an expandable sheath over the innermost portion of the device.
The sheath, typically made of a silicone polymer material or the like, has hydrodynamic properties of a quasi-isobaric inflation process which maintains a substantially constant pressure (P1) when inflated without external constraints (similarly to an inflatable balloon), which could typically be in the order of about 0.8 psig (about 5.5 kPa relative pressure). However, when constrained within the ear canal, the internal pressure rises and causes the in-ear device to overinflate and may injure or cause discomfort to the wearer of the device (at a pressure above a comfort-limit ear canal pressure level P2) when a settable compound is injected between the core and the sheath through an injection channel, which is in the order of about 2.0 psig (about 14 kPa relative pressure).
In the prior art, although the injection pressure was attempted to be controlled through human intervention, the pressure inside the in-ear device was difficult to control and monitor, as exemplified in U.S. Pat. No. 6,687,377 and in U.S. patent application No. 2005-0123146A1 tentatively try to solve that problem of limiting the maximum pressure level by assessing in situ the acoustic attenuation of the in-ear device during the inflation mode. Furthermore, such a process required a person duly trained to inject the settable compound, which is relatively expensive in addition to the fact that an appointment may be required.
In areas of application in the industry, it is important to obtain proper fitment for achieving consistent results in both hearing aid and hearing protection applications.
Accordingly, there is a need for an improved settable compound delivery system or apparatus for an inflatable in-ear device.